Organic and inorganic corrosion inhibitors have been used for many years to reduce corrosion of metals in contact with aqueous systems, such as mild steel in industrial heat exchange equipment and/or copper and copper alloys in contact with water treatment systems. It is important that such inhibitors used for corrosion protection be as safe to use as possible and be environmentally friendly. Over the years, the pursuit of a “green” corrosion inhibitor has led to the introduction of a variety of commercial products based on different inhibitor chemistries. The use of many of these chemistries has since been restricted by evolving environmental regulations.
Oxidizing biocides like sodium hypochlorite are used to reduce biological problems in cooling systems. This can minimize loss of heat transfer and health related issues like Legionella pneumophila. Formation of biological slimes can lead to under-deposit corrosion and efficiency loss due to a combination of organic and inorganic scale deposits. Although oxidizing biocides perform the necessary function of minimization of biological problems, they are also known to reduce the efficiency of some scale and corrosion inhibitors.
There is a continuing need for safe and effective water treatment agents which can be used to control corrosion, particularly when a substantial concentration of dissolved calcium is present in the system water. Water treating agents of this type are particularly advantageous when they are substantially free of heavily regulated metals, such as chromate, zinc and molybdate. Such treatment agents should desirably be able to function without substantially decreased performance in the presence of the type of oxidizing materials, such as sodium hypochlorite, that are often added as a biocide to water treatment and handling systems.